Martin Crieff was born in approximately 1977, to Wendy Crieff and a father on unknown name, who was an electrician. Presumably his birth took place in Wokingham and quite possibly in the same hospital that his mother is taken to in the eponymous episode. He is the second of three children; he has a younger sister named Caitlin ("Cat"), who works as a Traffic Warden, and an older brother, Simon, who is employed by the counci as a senior administrator . Although both siblings frequently mock Martin, they are believed, by their mother at least, to be "terribly fond" of him (Wokingham).

Before the age of six, Martin wanted to be an aeroplane; however, upon realising how unfeasible this was, he instead aspired to become a pilot (Fitton). Despite this long-term ambition, none of his family are particularly impressed by his profession (it is debatable as to whether or not this is the term to use, see Qikiqtarjuaq), his late father especially. Little is known of his school life, but it is probable that he may have been bullied or teased. In Kuala Lumpur he unknowingly reveals that he was left out of the secret clubs during lunch break, and his abiding memory of Nathan Smiley, a podiatrist that he and Simon went to school with, (Wokingham) is that "he threw [Martin's] briefcase on the science block".

In spite of his family's disapproval, Martin persisted with his ambition to pursue a career in flying. Undeterred by the flying school rejection, instrument rating failure, and seven goes it took him to get his licence (Abu Dhabi), he "did menial jobs and night shifts to save up for the flying hours" (Helsinki). His father died at an unknown point during his early adulthood, before he joined MJN Air. As discovered in Limerick, the late Mr. Crieff was especially critical of Martin's career options, and instead of leaving him money as he did Simon and Caitlin (who got £5000 each), left him his van, toolkit and multimeter, fearing that any money would be spent on pursuing his ambition. Although Martin is initially disappointed, the van later comes in useful when he sets up Icarus Removals, in order to earn money.

Two months after his father's death, Martin gets his first job as a pilot, which, although he concedes "was a rubbish job as a pilot", he also finds it frustrating that his father was unable to witness his first success.

Martin is so totally obsessed with aviation that he can scarcely think of any other conversational matter and reveals he relaxes at home by playing Microsoft Flight Simulator Edition 95. He also struggles to chat to the workers at Fitton Airfield in the illegal pub, The Flap and Throttle without "talking shop" and having to buy everyone a drink. He even incurs a "Whoops Johnny" for a consecutive offence and mentioning the "A-Word" (aviation).

Martin is not very good at sticking up for himself which results in a lot of teasing from Douglas. Almost everything he does goes wrong and he now naturally waits for Douglas's sarcastic comments.

He is a perfectionist, a characteristic he would say is his worst quality. (If that's too conventional, it's apparently the fact he's not very good at flying aeroplanes). Martin gets panicky very easily and finds it hard to stay relaxed, something he continuously denies, ironically whilst shouting hysterically.

Martin is rather self conscious, a problem which is not helped by teasing from Douglas, being patronized by his dominating brother, being mistaken for First Officer and intimidated by many passengers, especially Mr. Leeman who actually made him cry and the obsessive fourteen year old nephew of Carolyn, Kieran.

He is also not particularly good at conversing with women and has many awkward encounters with female passengers including: actress Hester McCaulay; the nature trip organiser from Unbeaten Track, Nancy Dean Liebhart; First Officer Linda Fairburn; and Captain Deroche from Swiss Airways.

He has had three girlfriends (enough for a petanque team) until it seems he might have found the love of his life during a trip to Vaduz. He manages to pluck up the courage to ask HRH Princess Theresa of Liechtenstein to go to Duxford Air Museum with him. This apparently went well and she invited him to a party at the Taj Mahal. The difference in date locations leaves Martin a little embarrassed but nonetheless, he now has a bobsleigh team.

It's been speculated that Martin has Asperger's Syndrome, and in his personal blog, John Finnemore confirmed that Martin indeed does have it. Since it was never mentioned directly in the show, he said that it was "present, but undiagnosed."

Martin is rather short, something he is frequently teased about and claims he is tall but as once said by Carolyn, the tape measure tells a different tale. In Rotterdam he is referred to as "Little Martin" which enrages him tremendously.

Douglas describes Martin sarcastically as having strong neck muscles which he has developed from wearing his heavily decorated Captain hat. Martin's hat is a common topic of Douglas's remarks. It is supposedly adorned with a ridiculous amount of gold and looks very silly. Even more so when a lemon is taped to it or when its decorated with raw spaghetti holding up cooked spaghetti.

Martin also suffers from a slight abnormality of the inner ear and can't go swimming without earplugs. It is, however, perfectly air-worthy.

Martin is often portrayed in paintings with ginger hair, although this is never actually mentioned.

"Yes, I do. I like it. Like you. I mean I like it like you do, not I like it like I like you, I don't like you. I mean I don't not like you, I just... I don - I don't like you as much as I like being a pilot."
-Newcastle

"Captain der-der-DER-der-der. That’s what you need. Not Captain der-der-DER…ff." -Rotterdam